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104 lines
2.2 KiB
PHP
104 lines
2.2 KiB
PHP
<?php
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/**
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*
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* @package phpBB3
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* @copyright (c) 2010 phpBB Group
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* @license http://opensource.org/licenses/gpl-license.php GNU Public License
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*
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*/
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/**
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* @ignore
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*/
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if (!defined('IN_PHPBB'))
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{
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exit;
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}
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/**
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* Cron lock class
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* @package phpBB3
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*/
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class phpbb_cron_lock
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{
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/**
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* Unique identifier for this lock.
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*
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* @var string
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*/
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private $cron_id;
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/**
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* Tries to acquire the cron lock by updating
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* the 'cron_lock' configuration variable in the database.
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*
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* As a lock may only be held by one process at a time, lock
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* acquisition may fail if another process is holding the lock
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* or if another process obtained the lock but never released it.
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* Locks are forcibly released after a timeout of 1 hour.
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*
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* @return bool true if lock was acquired
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* false otherwise
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*/
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public function lock()
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{
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global $config, $db;
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if (!isset($config['cron_lock']))
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{
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set_config('cron_lock', '0', true);
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}
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// make sure cron doesn't run multiple times in parallel
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if ($config['cron_lock'])
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{
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// if the other process is running more than an hour already we have to assume it
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// aborted without cleaning the lock
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$time = explode(' ', $config['cron_lock']);
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$time = $time[0];
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if ($time + 3600 >= time())
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{
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return false;
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}
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}
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$this->cron_id = time() . ' ' . unique_id();
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$sql = 'UPDATE ' . CONFIG_TABLE . "
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SET config_value = '" . $db->sql_escape($this->cron_id) . "'
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WHERE config_name = 'cron_lock'
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AND config_value = '" . $db->sql_escape($config['cron_lock']) . "'";
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$db->sql_query($sql);
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// another cron process altered the table between script start and UPDATE query so exit
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if ($db->sql_affectedrows() != 1)
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{
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return false;
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}
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return true;
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}
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/**
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* Releases the cron lock.
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*
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* The lock must have been previously obtained, that is, lock() call
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* was issued and returned true.
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*
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* Note: Attempting to release a cron lock that is already released,
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* that is, calling unlock() multiple times, is harmless.
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*
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* @return void
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*/
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public function unlock()
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{
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global $db;
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$sql = 'UPDATE ' . CONFIG_TABLE . "
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SET config_value = '0'
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WHERE config_name = 'cron_lock'
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AND config_value = '" . $db->sql_escape($this->cron_id) . "'";
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$db->sql_query($sql);
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}
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}
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